Preparation of thiocarbanilide and its homologs



Feb 3, i948,

H. 1.,. sTAssE PREPARATION OF THIOCARBANILIDE AND ITS HOMOLOGS Filed May 18, 1945 Patented Feb. 3, 1948 UNITED STATES PATENT oel-*lee 2335,295 PREPARATION QFHIRITS AND x'rs HoMoLoGs -Ien'y S'tss, .Haywthorne" Jg;

Allied chemical & Dye corporation', New verle N. Y., a corporation' of New Yo'rk u Appliction lvlay is, 1945", sial N6. 594,492"

v'AIhivs' invention *relates to the production of thiourea., derivatives, and more particularly -to an improved process for reacting aniline and.

zonscHlNHH; osi A cHo'dHlNHNHcHicHilF His However, thereactions,proceedslowly and unless a'd'ilu'en't suchaas alcohol is employed, the product's crystallize formingstiff masses *which cannot easilyrloe stirred, Various expedients have been proposed forthe purpose of Iincreasing the speed i the reaction andimprovingnthe .yields of the desired products. For example, it hasbeenpro.- posed toI add sulfur polysulndeslsulfur chlorides and pyridine to reaction mixtures for this pur- P@- M It isan oloject Vof this invention to provide an improved process for the manufactureof thiocarbanilide and methylzhomologs'thereof by reaction'oi aniline and toluidines, respectively, with carbondisulde.

u It isa further object of the invention to provide annoy/elA process of reacting carbon disulfide with aniline and toluidines whereby high yields of thioearbanilide and dimethylthiocarbanilides are obtained in relatively 'short reaction times;

Qther objects'and advantages will appearhereinafter.

In accordance withthe inventionycarbondisulfide is reacted With'aniline or toluidines; orA both of these types of these" amines; inthe presence oforga'nic base-material .containing the pyridine nucleus .boiling within the range of .150 toY 210 C. At least preferablyfrom 25% to 80%, oi organic bases containing the' pyridine nucleus based 0n the .Weight-ef the amine and at least .one m91; .preferably .imm H11/ato .2l/2.111015, 0f .Carbon disulfide -for each mol of amine areutilizved.

.l have fcurldthat byzcelryirg fmt. thereediep in the presence of such organic bases containing 9 claims. (cl. 26o-552) llzed'. s iigcii' mixtures are coilstitutedenieny of alkyl pY'ridn'S-.p lrilteald 0f mxine pfu or toliiidin ith' thla'lkyl pyridin'es,;tnese. mami rials ina'y'. `be simultaneously. extractedfroxn coal-t tarQd'Sftlll @Onlig Elem', .ef gl, .@CDOHC hinasnffacae, and the extfactebeses distilled maintain cui c ontjeiningyehe deslrapfopor en of aniline and@ pases' involving the pyridine nucleus. Eer example, I` have .found a`rfraction of; meedeed fwn coal. er boiling; what@ rangeof lgoei-,o 1,85 C. and containing 50% .to 80.0/ by' .weielit eflrlle, the. remainder beig' chiefly.' alkyl pynidiees', ne be eminently siiitabie for carrying out the invention. Fractions. of eqal tarbases` boiling within the ranlgeoflgro" to .23105 C.,y l containing similar percentages of ltolili'dines, remainder loing chieflylalkyl pyridine's may Tneeccompenyinedrawing iS. fLiv..S.it

v .municating with' centrifugel ell which. dischargesv through valved conduits into receivers 6' and 8. The reaction vessel is also equipped with a fractionating column I and a reux condenser I2 communicating with condenser I4 which discharges through valved conduits into either of two receivers I6 and I8 or directly to carbon disulfide scrubbers 20 and 22 containing aniline or toluidine. The carbon disulfide scrubbers communicate with hydrogen suliide scrubber 24 containing a solution of lime or caustic alkali, e. g., caustic soda, for absorbing hydrogen suliide liberated during 'the reaction. Reference numerals 26, 28, 30 and 32 designate containers for aniline (or toluidine), carbon disuliide, a solvent such as benzene and tar bases, respectively, which containers communicate with the reaction vessel through a valved conduit system as shown on the drawing, whereby the desired amounts of thesematerials may be introduced into the vessel. The conduit systemis Yarranged to permit discharge of aniline oretoluidinehfrom container 26 into either or both of carbon'disukr fide scrubbers 20 and 22. Y V K The invention may be carried out, for example, by reiiuxing aniline with, say 2 mols of carbon disulfide and about 25 to 80 percent, based on the weight of the aniline, of organic base material containing the pyridine nucleus boiling within the range of 150 to 210 C., preferably 160 to 190 C., while agitating the mixture slowly. Most of the carbon disuliide vapors are condensed in reflux condenser I2 and returned to the reaction Vessel, The remainder, together with the liberated hydrogen sulfide, are passed through the scrubbers 20, 22 containing aniline where the carbon disulfide is absorbed, The unabsorbed hydrogen sulfide passes to scrubber 24 where it is absorbed by caustic soda or lime solution, After vthe reaction is substantially complete, which ordinarily requires about 6 to 12'hours, the reaction mixture is cooled, e. g., to about -15 C., to crystallize the thiocarbanilide andv is then iiltered or centrifuged to separate the Y thiocarbanilide crystals from the mother liquor. The crystals are washed with a solvent such as benzene toY remove adherent mother liquor. The mother liquor is returned to the reaction vessel with suii'icient fresh aniline, tar bases and carbon disulde to 4 separate the benzene and bases from the impurities which are left as residue. The purified bases may be re-utilized in the process. The distillation may be conducted in reaction vessel I and the benzene and tar bases collected separately in receivers I6 and I8.

When a tar-base fraction containing the desired proportions of aniline and tar bases involving the pyridines nucleus is utilized, the reaction may be carried out as hereinabove described and when it is complete the unreacted carbon disulfide is distilled of from the' reaction mixture, preferably at a temperature not above 100 C., and collected in receiver I6 or I8. From 100% to 200% of benzene based on the weight of the aniline content of the tar-base fraction is added to the mixi ture, the mixture is then cooled, e. g., to 5-15 C., to crystallize the thiocarbanilide and the crystals are separated from the liquor by centrifuging or filtration. ,s The benzene is separated from the .tar bases by distillation at a temperature not above 130C. and the bases and thiocarbanilide dissolved therein may then be recovered by vacuum or steam distillation and treatment with benzene as described in the preceding paragraph. The recovered bases may be utilized in any desired manner. L For example, they may be employed in conjunction with substantially pure aniline and carbon disulfide for thiocarbanilide production. If the thiocarbanilide crystals have an objectionable odor or contain objectionable impurities, they may be furtherpuried by recrystallization from a solvent such as benzene.

When using tar base mixtures of high aniline content, i. e., 75% or more, the reaction mixture may be diluted with a suitable solvent before carrying out the reaction. This procedure facili.. tates agitation of the heavy slurry of crystals which is produced. As diluents, aliphatic, acyclic and aromatic hydrocarbons, preferably suiiiciently volatile to permit ready removal thereof from the tar bases by distillation, may be employed.

A Aromatic hydrocarbons such as benzene, toluene give the desired proportions of materials and the reaction repeated. The aniline-containing absorbed carbon disulfide from the carbon disulfide scrubbers 2U and 22 may furnish a portion of the aniline and carbon disulfide content of the reaction charge.

' The tar bases containing the pyridine nucleus may be used repeatedly in this manner until impurities build up to an extent such that they objectionably affect the quality of the thiocarbanilide, whereupon the mother liquor is distilled in the reaction vessel, preferably at a temperature not above 100 C., to separate carbon disulfide therefrom.l The liquor is then subjected to distillation under vacuum (absolute pressure of from 1" to 2f( of mercury) or steam distillation toremove vthe tar bases, and the distillation is discontinued when a thick mass of thiocarbanilide crysand xylene and mixtures thereof are preferably employed lfor this purpose. Such solvents may also be utilized instead of benzene in the procedure hereinabove described.

The above procedure is also applicable to the reaction of toluidines with carbon disulfide to produce dimethyl-thiocarbanilides Y The following examples are further illustrative of the invention:

AEozcmzple 1,-200 partseby Weight of aniline, parts by weightof" a mixture of alkyl pyridines boiling Within the range of to 185 C. and 250 parts by weight of carbon disulfide were reuxed together in a reaction vessel equipped with a reflux condenser and an agitator for 8 hours while agitating. the reaction mixture slowly. The vapors escaping from the reiiux condenser were passedthrough a scrubber containing aniline to absorb the carbon disulfide and then through a scrubber in which an aqueous solution of sodium hydroxide was circulated to absorb the hydrogen sulfide. The reaction mixture was then cooled to 5 to 10 C. to crystallize the thiocarbanilide, iiltered to separate the crystals from the mother liquor and the crystals were washed with benzene and dried at 60 to 65 C. The mother liquor was returned to the reaction vessel together with the aniline (containing carbon disulfide) fromA the carbon disulfide scrubber and sufficient additional aniline and carbon disulfide to form the desired reaction mixture, and the above procedure was ademas cooled vto .-'15 G. Eer this .purpose :benzene which hasv previously ,been used for Washing thiocarbanildc crystals may befemployed.- l'lhe liquor' was filtered tov separate-.the .crystals .therefrom and was then distilled at atmospheric prs;- 'sure at a still temperature not exceeding 130 C. to separate the benzene from the tarbases. zThe residue.: Was' `fractionated under-abso1ute pressure of 1" 'of mercury at a still temperature not exceeding 130 C. and the residual benzene and tar bases were collected separately as distillate. The distillation was discontinued when a heavy mass of thiocarbanilide crystals formed. Suicient benzene was added to the crystals to form a slurry, the mixture cooled to 515 C., filtered, the crystals washed With benzene and dried at 60 to 65 C. The filtrate containing the benzene and a small amount of tar bases was fractionally distilled irst at atmospheric pressure and then under absolute pressure of about 1" of mercury to separate the benzene and bases from the impurities which remained as residue. From 95% to 98% of the theoretical yield of thiocarbanilide crystals having a melting point of 153 to 153.5 C. Were obtained. Y

Example 2.-250 parts by Weight of a fraction of tar bases boiling Within the range of 180 to 185 C. containing 78% by weight of aniline and 22% of tar bases involving the pyridine nucleus- Were reacted with 250 parts of carbon disulde as described in Example 1. The unreacted carbon disulfide was then removed from the reaction mixture by distillation at a still temperature not exceeding 100 C., and 250 parts by weight of benzene were added to the mixture which was then cooled to C. The mixture was iltered to separate thiocarbanilide crystals from the liquor, the crystals were washed with benzene and dried at 60 to 65 C.

The mother liquor ltrate was distilled under atmospheric pressure at a temperature not exceeding 130 C. to separate benzene therefrom, the residue was fractionated under pressure of 1" of mercury at a still temperature not exceeding 130 C., and the tar bases and residual benzene were collected separately as distillate. The distillation was discontinued when a heavy mass of thiocarbanilide crystals formed, suiicient benzene Was added to slurry the residue, the mixture was cooled to 15 C., iltered, and the crystals washed with benzene and dried at 60 to 65 C. A thiocarbanilide yield of 98% of theoretical Was obtained. The thiocarbanilide crystals had a melting point of 153 to 153.5 C. The filtrate Was distilled under vacuum to separate the benzene and the remainder of the bases from irnpurities, which remain in the still as residue. The recovered bases may be employed for any desired purpose. For example, they may be utilized in conjunction with substantially pure aniline for the production of thiocarbanilide.

Thus it will be seen that the invention provides a novel process for reacting aniline and toluidines with carbon disulde to obtain high yields of thiocarbanilide and dimethyl-thiocarbanlides in a relatively short reaction time. As hereinabove pointed out, substantially higher yields of 6 reactionproducts.are.obtanablerifashdrtr e action time than are obtainable if bases oo rrain,c ine the-pyridinenucleus boiling-belen .15.01Q.. 0r above 210 .0, .are utilized. The boiling points referred -toherein are, .at `pressure .oi 76o mercury.

vsince.certain changes maybe made without departing trom the scope ci the invention, vitis intended-that. the; .ancre shall; .be interpretadas -illustratireandnot a .11.. tif.

Iclaimz.` VVV1. .A pl'ocess fors- ;thepraduction.of .at-.member 0f :the group. consisting or Vthiocarbanilide and methyl homologs. which `comprises reacting :a member of the group consisting of aniline and toluidineswith carbon disulde in the presence of organic bases containing the pyridine nucleus boiling within the range of to 210 C.

2. A process of producing a member of the group consisting of thiocarbanilide and dimethylthiocarbanilides which comprises reacting an amine of the group consisting of aniline and toluidines with carbon disulfide in the presence of from 25% to 80%, based on the Weight of the amine, of organic bases containing the pyridine nucleus boiling within the range of 150 to 210 C. with from 1 to 21A; mols of carbon disulde for each mol of the amine, and heating the mixture until the reaction is substantially complete.

3. A process of producing thiocarbanilide as defined in claim 2 in which the amine is aniline, said process including the further steps of cooling the reaction mixture to crystallize thiocarbanilide, separating the crystals from the liquor and reacting additional carbon disulde and aniline in the presence of the liquor.

4. A process of producing thiocarbanilide which comprises mixing carbon disulde with a mixture of aniline and'from 25% to 80%, based on the Weight of the aniline, of organic bases containing the pyridine nucleus, said bases boiling Within the range of from 150 to 210 C., the car- -bon disulfide being present in proportions of from 1 to 21/2 mols for each mol of the aniline, and refluxing the reaction mixture for from 6 to 12 hours.

. 5. A process as dened in claim 4 involving the additional steps of separating unreacted carbon disulfide from the reaction mixture, adding benzene to the reaction mixture and cooling the mixture to crystallize thiocarbanilide.

6. A process as dened in claim 4 involving the additional steps of separating unreacted carbon disulfide from the reaction mixture, adding benzene to the mixture, cooling the mixture to crystallize thiocarbanilide, separating the crystals from the liquor, and distilling the liquor at a temperature not exceeding 130 C. to recover the benzene, tar bases and additional thiocarbanilide.

7. A process of producing thiocarbanilide which comprises mixing carbon disulfide with a coaltar-base fraction constituted substantially of aniline and from 25% 110.80%, based on the weight of the aniline, of bases containing the pyridine nucleus boiling within the range of from to C., the carbon disulfide being present in proportions of from about 1 to 21/2 mols for each mol of the aniline, reuxing the mixture until the reaction is substantially complete, distilling the mixture at a temperature not exceeding 100 C., until unreacted carbon disulde is substantially completely removed therefrom, diluting the mixture with benzene, cooling the mixture to a temperature not above 15 C. to crystallize thiocarbanilide, and sebarting the crystals from the liquor. 8. A process as defined in claim 7 involving the additional steps of distiiling the liquor at a tem- -perature not above 130 C. to separate benzene therefrom, distilling the residue under vacuum at a. temperature not exceeding 130 C. to remove the tar bases and crystallize substantially all of the thiocarbanilide, adding sumcent benzene to the crystals to form a slurry and iiltering the slurry to separate the crystals from the benzene.

9. A process as dened in claim 7 in which the rreaction between the carbondisulflde and anillne -is carried out in the presence of benzene.

HENRY L. sTAssE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,477,804 Bedford et al Dec. 18, 1923 1,482,317 OBrien Jan, 29, 1924 1,549,426 Weiss Aug. 11, 1925 2,106,552 Jenkins et a1 Jan. 25, 1938 1,688,707 Hand et a1 Oct. 23, 1928 FOREIGN PATENTS Number Country Date 307.906 Great Britain Feb. 20, 1930 

